Production of colored photographic images by color-development



Patented Oct. 16, 1945 PRODUCTION OFCOLORED PHOTOGRAPHIC IMAGES BY COLOR-DEVELOPMENT Bruno Gluck, Elstree, England, assignor to Dufay- Chromex Limited, London, England, a British comp any No. Drawing. Application July 10, 1944, Serial No. 544,329. In Great Britain May 26, 1943 Claims.

This invention is for improvements in or relating to the production of colored photographic images by color-development.

There is known a process of producing color pictures in which an exposed silver halide emulsion is developed in the presence of a substance known as a color-former," the color-former being a substance which reacts with the oxidation products of an aromatic amino photographic de veloper to form a colored image which can be revealed by bleaching out the silver image with Farmer's reducer or with other suitable photographic bleaching agent.

The property of color-formers to couple with the oxidation products of aromatic amino photographic developers may be ascribed to the presence in the color-former compounds of active groups which are conveniently termed coupling functions. The commonly known coupling functions include (1) a phenolic hydroxyl group, as for example in a-naphthols, (2) an aromatic amino group as in p-phenylene diamine, and (3) an active methylene group in (a) an open chain, as in aceto-acetic esters, or in (b) a heterocyclic nucleus as in a pyrazolone, or (c) adjoining a cyano group, as in p-nitro-benzylcyanide.

In the production of photographic color images utilising color-development a number of physical and chemical properties are required of the colorformer additional to the power of coupling to produce colored images described above. Such additional properties may include non-diffusibility from the emulsion or other layer, absence of deleterious effect on the speed fog and contrast of the silver halide emulsion in which it is dispersed, the production of coupled dyestuffs of desired hue and of a suitable degree of insolubility in water.

On account of the number of these requirements, which vary with the exact nature of the process employed, it has not always been possible to select from the many substances which have already been proposed, color-formers which are entirely suitable for a particular procedure.

We have now discovered that improved results may be obtained in a process of producing colored images by use of a new series of colorformers conforming to the requirements abovereferred to.

According to the present invention, there is provided a process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group in conjunction with color-former in which the coupling function as above-defined occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means of one sulphur atom.

The color-former may be incorporated in the emulsion 0r mixed with the aromatic amino-developing agent, e. g. an aromatic diamino compound, using for this purpose a solution in an alcohol, for example in methyl or ethyl alcohol, or other suitable solvent or solvent mixture or again the color-former may be incorporated in a layer adjacent to one comprising a reducible silver halide emulsion.

Color-formers employed in accordance with the present invention include the following:

Omroo CoNHO CH.S.C

CHa.CO CO.CHs

Thio-bis-acetoacetic anilide giving a yellow image on color-development.

2. C2H5O.CO CO.OC2H5 CH.S.C

0133.00 00.0113 Thio-bis-acetoacetic ester giving a yellow image on color-development.

N is.

Thio-bis-phenylmethylpyrazolone giving a re image on color-development. 4. CH3(fi-CH-S-(3H-fiCHs acetanilides with an inorganic halogen compound such as sulphur dichloride or thionyl chloride. It is preferable to employ thionyl chloride to sulphur dichloride since sulphur dichloride acts as a powerful desensitiser for the emulsion and if used for the preparation of the colorformer very thorough purification of the product is essential.

When the color-formers made by the present invention are basic they may be used as such or in the form of the corresponding inorganic acid salts. 1

jlollowing is a description by way of example of two methods of carrying the invention into effect.

Exmm: I

Thin-bis-(1-phenyl-3-methyl-S-pyrazolone) To 5 grams of 1-phenyl-31-methyl-5-pyrazolone dissolved in 50 cc. of chloroform 2.2 cc. of thionyl chloride were added. After standing for three days the solid was filtered oil, liquid removed by pressing on the funnel and the partially dried solid washed with a little dry ether to remove any thionyl chloride still present. It

was then recrystallised several times from methylalcohol and refluxed for 6 hours in absolute alcohol to which animal charcoal had been added. The clear filtrate was then allowed to cool after adding an equal amount of dry light petroleum ether. The resulting color-former consisting of thio-bis- 1-phenyl-3-methyl-5-pyrazolone) consisted of small white crystals. having a melting point of l81-2 c. l

5 grams of the color-former prepared as described above were dissolved in 50 cc. of ethylene glycol and 50 cc. of methyl alcohol and the solution was mixed with an aromatic amino-developing solution consisting of: N-N-diethyl-p-phenylenediamine hydrochloride grams Sodium sulphite cryst -do 20.0 Sodium carbonate cryst --do 40.0 Water to or 1,000

Thio-bis-acetoacetanilide 8.75 grams of acetoacetanilide were dissolved in 150 cc. dry benzene and 1.66 cc. sulphur dichloride added drop by drop. After standing for 3 days the solid was filtered on, liquid removed by pressing on the funnel and the partially dried solid washed as before with a little dry ether. It was then recrystallised several times from methyl alcohol and refluxed for 6 hours in carbon disulphide and for a further 6 hours in benzene to which animal charcoal had been added. The filtrate was then allowed to cool after adding an equal amount of dry light petroleum ether. The color-former consisting of white silky needles of thio-bis-acetoacetanilide had a melting point of 146 C.

5 grams of the color-former prepared as described above were dissolved in 50 cc. of ethylene glycol and 50 cc. of methyl alcohol and the solution was mixed with anaromatic amino-developing solution consisting of:

N -N -diethyl-p-phenylenediamine hydrochloride grams 2.5 Sodium sulphite cryst do 20.0 Sodium carbonate cryst -do 40.0 Water to cc 1,000

lhe mixed solution of coupler and developing agent was employed as a developer for a silver halide photographic emulsion in the production of a colored image as described in Example I.

I claim:

1. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means of a single sulphur atom.

2. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means or a single sulphur atom, the said color-former being incorporated in the emulsion.

3. A process for the development or a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means of a single sulphur atom, the said color-former being mixed. with the amino-developing agent.

4. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic diamino-develop' ing agent containing a primary amino group in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means of a single sulphur atom.

5. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic diamino-developing agent containing a primary amino group in conjunction with a'color-former in which the coupling function occurs at least twice and in which at least two oi the active methylene groups constituting the coupling functions are directly linked by means of a single sulphur atom, the said colorformer being incorporated in the emulsion.

6. A process for the development of a reducible silver salt emulsion to produce a colored image whichprocess comprises developing the emulsion by means of an aromatic diarnino-developing agent containing a primary amino group in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting the coupling functions are directly linked by means of a single sulphur atom, the said colorformer being mixed with the diamino-developing agent.

7. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group consisting of an N-N-dialkyl-p-phenylenediamine in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting said coupling functions are directly linked by means of a single sulphur atom.

8. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group consisting of an N-N-dialkyl-p-phenylenediamine in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting said coupling functions are directly linked by means of a single sulphur atom, the said colorformer being incorporated in the emulsion.

9. A process for the development of a reducible silver salt emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group consisting of an N-N-dialkyl-p-phenylenediamine in conjunction with a color-former in which the coupling function occurs at least twice and in which at least two of the active methylene groups constituting said coupling functions are directly linked by means of a single sulphur atom, the said colorformer being mixed with the said N-N-dialkyl-pphenylenediamine developing agent.

10. A process for the development of a reducible silver halide emulsion to produce a colored image which process comprises developing the emulsion by means of an aromatic amino-developing agent containing a primary amino group in conjunction with a color-former consisting of thio-bisacetoacetic anilide N H.co /CO.NHC

onscn 0H,. 0 o c 0.011:

BRUNO GLUCK. 

